The purpose of the present study is to investigate the regulation of the host cell epigenetic machinery by metabolic products from periodontal bacteria and the impact on enhancing viral replication and infection in the oral cavity of HIV patients. It s well established that HIV patients exhibit increased prevalence and severity of chronic periodontitis and endure more frequent infections by herpesviruses such as herpes simplex virus (HSV), Epstein Barr virus (EBV), and Kaposi sarcoma-associated herpesvirus (KSHV). The oral cavity is also a potential reservoir for latent HIV infection. Previous studies suggest tht periodontal bacteria promote lytic replication of both HIV and herpeviruses, resulting in recurrent HIV infection and oral lesions. Anaerobic gram- negative bacteria produce various short chain fatty acids (SCFAs) that inhibit class-1/2 histone deacetylases (HDACs) to promote histone hyperacetylation and viral gene expression. However, whether SCFAs impact other epigenetic regulators and whether they also enhance viral infection have not been studied and remain to be determined. Data from our pilot study indicate that SCFAs not only induce lytic replication of HIV and KSHV but also increase the infection rates of the two viruses in their respective target cells. Besides inhibition of class-1/2 HDACs, SCFAs also down regulate expression of the class-3 HDAC SIRT1 and the subunit EZH2 of the polycomb repressive complex (PRC2), leading to histone hyperacetylation and reduction of repressive histone methylation simultaneously. Based on these results, we hypothesize that SCFAs modulate multiple epigenetic regulators to promote lytic replication of both HIV and herpesviruses such as KSHV in the oral cavity. We believe that SCFAs also impact the host cytoskelton and transport pathways to make cells more permissive to viral infection. A high throughput shRNA library screening for epigenetic regulators involved in HIV transcriptional activation has led to our identification of a number of epigenetic regulators that appear to form multi-protein silencing complexes. To test our hypotheses, in AIM-I, we will perform proteomic analysis to identify the specific components of the epigenetic silencing complexes and examine the effects of SCFAs on expression of the regulators in oral epithelial, endothelial, and CD4+ T- cells. We will also confirm the roles of the SCFAs-regulated epigenetic regulators in transcriptional activation of both HIV and KSHV in our model systems. Previous studies suggest that lysine acetylation of cytoskeleton actins and microtubule plays important roles in viral entry and intracellular trafficking. In AIM-II, we will examine if and how SCFAs cause lysine acetylation of cytoskeleton actins and microtubule to increase viral infectivity, as a consequence of SCFAs suppression of both class-1/2 HDACs and class-3 HDAC SIRT1. To further test our hypotheses, in AIM-III, we will examine if oral epithelial and T cells from HIV-patients with severe periodontal disease indeed display SCFAs-related epigenetic changes detected in AIM-I, and whether the epigenetic changes correlate with viral replication and infection in the patients, by conducting cross sectional and longitudinal human studies. It is expected that the present study will reveal novel and common mechanisms that control replication and infection of both HIV and herpesviruses in the oral cavity of HIV patients. The results should provide a scientific basis for developing novel strategies to prevent and treat recurrent HIV and herpesviral infections in HIV/AIDS patients simultaneously.